083 inch thick.
220 " 0.095 "
240 " 0.109 "
250 " 0.120 "
320 " 0.134 "
610 " 0.148 "
1,450 " 0.165 "
Some of the iron was of the very poorest quality; the pipe was made by
contract in San Francisco, without the supervision of an inspector, as the
contractors were a firm of good reputation; the bad quality of the iron
was not detected until too late to have it corrected. Since then, the
writer has always had such pipes--the mines of which he has been the
manager using large quantities--made directly on the ground where they are
to be used; the pipe makers, in the latter case, always reject such sheets
as are too much below in thickness the standard gauge, and those which
show in passing through the rolls the bad quality of iron; tests of each
joint by hydrostatic pressure would add too much to the cost.
[Illustration: FIG. 16.]
The maximum tensile strain upon each of the seven thicknesses of iron used
was intended to be 16,500 pounds per square inch. Some of the sheets were
below the standard gauge, so that, in reality, the tensile strain is
sometimes as high as 18,000 pounds. The mean diameter of the pipe was
1.
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